Skip to Main content Skip to Navigation
Theses

Dynamiques non linéaires dans les fibres multimodes à gradient d’indice : Caractérisation spatiotemporelle/ spectrale, et applications à la génération de supercontinuum MIR

Abstract : This thesis describes the use of graded index multimode fibers (GIMF) for the improvement of laser systems. In the last few years, these fibers have seen a revival of interest in particular in spatial multiplexing telecommunication systems or for the realization of optical components. In the high intensity regime, it was demonstrated recently that the self-imaging process endured by the beam propagating in these fibers allows for the emergence of new spatial, temporal and spectral non-linear dynamics. The self-cleaning of the beam by the Kerr effect, which transforms a multimode beam (speckle) into a quasi-Gaussian beam, is a spectacular manifestation of this effect. This thesis extends our understanding of this phenomenon by demonstrating Kerr beam self-cleaning in the weakly multimode regime. I also proposed a new technique for time-resolved observation of the nonlinear dynamics. In particular I was able to identify the various modes involved in the intermodal couplings with a time resolution as short as 8 ps. Finally, I showed that a low energy single mode beam can trigger the self-cleaning phenomenon on a second high intensity multi-mode beam, with a longer term application to the realization of all-optical logic gates. Beam self-imaging in a GIMF is also accompanied with the generation of parametric lines far detuned from the pump. In a second part of this thesis, I focused on these nonlinear space-frequency dynamics. First, I have characterized the modal content of the parametric lines, which had not been done before. Then, I exploited the high power spectral density of these parametric lines strongly shifted from the pump wavelength to generate an intense supercontinuum in the mid-infrared from a 1 μm laser, for the first time to my knowledge. Finally, I have studied the conditions for optimizing the spectral extent of the mid-infrared continuum and demonstrated that a judicious choice of the input beam characteristics allows to cover three octaves, from 0.75 to 6 μm.
Document type :
Theses
Complete list of metadata

https://tel.archives-ouvertes.fr/tel-03629672
Contributor : ABES STAR :  Contact
Submitted on : Monday, April 4, 2022 - 2:58:09 PM
Last modification on : Tuesday, April 5, 2022 - 3:36:39 AM
Long-term archiving on: : Tuesday, July 5, 2022 - 6:46:15 PM

File

2022LIMO0017.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-03629672, version 1

Collections

Citation

Yann Leventoux. Dynamiques non linéaires dans les fibres multimodes à gradient d’indice : Caractérisation spatiotemporelle/ spectrale, et applications à la génération de supercontinuum MIR. Optique / photonique. Université de Limoges, 2022. Français. ⟨NNT : 2022LIMO0017⟩. ⟨tel-03629672⟩

Share

Metrics

Record views

47

Files downloads

1